Open water swimmers are warned of a potentially dangerous condition that causes fluid in the lungs.
Doctors writing in the BMJ Case Reports journal said swimmers should be educated more about the risks of swimming-induced pulmonary edema (SIPE), which has been linked to swimming in cold water.
They said the condition leads to fluid buildup in the lungs, resulting in shortness of breath, low oxygen levels in the body, and coughing.
Open water swimming is a popular sport, with more than three million people thought to take part each year in England, they said.
However, SIPE cases are likely to go unreported and often occur in people who are otherwise fit and healthy.
Factors that increase risk include being older, being a woman, having high blood pressure, swimming long distances, colder temperatures, and pre-existing heart disease.
Doctors, Royal United Hospitals Bath NHS Foundation
Trust, describe the treatment of a woman in her 50s who is an enthusiastic swimmer and competitive long-distance triathlete.
He was otherwise in good shape, having difficulty breathing and coughing up blood after participating in an evening open water swimming event with water temperatures of around 17C while wearing a wetsuit.
His symptoms started after swimming 300 meters.
The woman had experienced breathing difficulties during an open water swim a fortnight earlier, forcing her to leave the event and leaving her breathless for a few days afterwards.
Upon arrival at the hospital, his heartbeat was rapid and a chest X-ray revealed pulmonary edema, doctors said.
Other scans showed that fluid had seeped into his heart muscle and caused strain, but he did not have structural heart disease.
The woman’s symptoms subsided within two hours of her arrival at the hospital, but she was monitored overnight and released the next morning.
Experts said it’s unclear exactly what causes SIPE, but it’s likely related to how the blood responds to a cold environment, combined with exaggerated constriction of blood vessels in response to cold and increased blood flow. during physical exertion.
They suggested that recurrence is common and has been reported in 13%-22% of divers and swimmers.
As advice for swimmers, the doctors said people should consider swimming at a slower pace, not wearing a tight-fitting wetsuit in warmer temperatures and avoiding tablets such as ibuprofen.
For those experiencing symptoms for the first time, the authors recommend stopping swimming and getting out of the water immediately, then sitting upright and calling for medical help if necessary.
Writing in the diary, the woman said: “While swimming in a quarry in an overnight swim, I began to hyperventilate and realized I couldn’t swim anymore.
“Luckily, I was able to call for help and a paddle board guided me back to the pier. When I got out, I unbuttoned my wetsuit and immediately felt the sensation of fluid filling my lungs.
“I started coughing and had a metallic taste in my mouth. When I got into the light, I could see my sputum was pink and frothy.”
She said her husband took her to A&E for treatment.
“Two weeks prior to this incident I had experienced a much milder event while swimming in open water in the sea that I had not attributed to SIPE at the time, but had also experienced difficulty in my normal pool swimming and running training.
“I just assumed it was a little under the weather. Other than this I have had no other symptoms and am now fully recovered and back to full training.”